Wireless communication systems have been commonly employed to provide voice and data communications to subscribers within prescribed geographic areas. For example, analog cellular telephone systems have been deployed successfully throughout the world. Recently, digital cellular systems such as those specified in the “IS-136” standard for North America and the Global System for Mobile (GSM) standard in Europe, North America, and elsewhere have been deployed. Attempts to unify and modernize the global, mobile communications networks have culminated in the so-called “3G” or third generation standards. These standards call for a wide-band code division multiplexed access (WCDMA) communication system. A subscriber terminal for this system is referred to as an “universal mobile telecommunication system” terminal, or simply a “UMTS” terminal. 3G and UMTS are just beginning to be deployed, and are extensively discussed in the International Telecommunication Union (ITU) Standard IMT-2000, the most recent version of which is incorporated herein by reference.
FIG. 1 illustrates a typical wireless communication system according to any of the standards, including IMT-2000. In FIG. 1, communication system 20 includes one or more wireless mobile terminals 22 that communicate with a plurality of cells 24 served by base stations 26 and a mobile telephone switching office (MTSO) 28. Only three cells are shown for clarity, but a typical network would include hundreds of Users of mobile communication system 20 can communicate with users of traditional, landline telephones 32 through the public switched telephone network (PSTN) 34.
Determining the location of a subscriber within a mobile communication system has been a challenge for many years. Location determination can be important for locating a subscriber who has made an emergency call. Often, subscribers using mobile phone systems are not familiar with the locale, and may not be able to describe a location to emergency service personnel. Numerous proposals have been introduced to provide location determination capability to the wireless telecommunication infrastructure. One proposal, which has been implemented in a limited fashion, is to use the global positioning system (GPS) for determining the location of mobile terminals. GPS is a space based triangulation system using satellites and computers to measure positions anywhere on earth. GPS signals have similar, or narrower bandwidths than UMTS or CDMA2000 (a second generation wireless standard) digital wireless telecommunication network signals. Therefore, GPS reception capabilities can be efficiently combined into UMTS and some second generation mobile terminals. However, because the satellites are always moving, position location algorithms are complex. Additionally, GPS signals are weak and may not always be received.
Proposals have recently been introduced to use digital television station signals as ranging signals for position determination in lieu of using GPS signals. Digital television was first implemented in the United States in 1998. As of the end of 2000, 167 stations were on the air broadcasting digital television signals. As of early 2001, over 1,000 digital television station construction permits had been acted on by the U.S. Federal Communications Commission. Therefore, digital television stations, 40 of FIG. 1, will eventually be disbursed adjacent to the wireless telecommunication network infrastructure, at least in the U.S., and probably in other countries. It is, however, difficult to receive digital television signals through the components of a typical mobile terminal, even a UMTS (also referred to as WCDMA) terminal. This difficulty results from the fact that digital television signals have a bandwidth that is wider than the bandwidth of mobile communication terminal signals.